Mercapto-containing organosilicon compounds are widely used as adhesion improvers for resins to inorganic substrates such as glass and metal materials. As described in JP 4692885, for example, mercapto-containing organosilicon compounds are added to epoxy resins for the purpose of improving the adhesion of the epoxy resin to a leadframe. Of the mercapto-containing organosilicon compounds, 3-mercaptopropyltrimethoxysilane and 3-mercaptopropylmethyldimethoxysilane are commonly used.
Since these mercapto-containing organosilicon compounds have low boiling points, they will volatilize off during high-temperature coating. Thus the mercapto-containing organosilicon compounds must be added more than the necessity. In addition, the surrounding equipment can be contaminated with the volatilizing compounds.